SULFUR REMOVAL USING FERROUS CARBONATE ABSORBENT
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This Invention relates to an absorbent composition useful for removing
sulfur-containing compounds from a variety of fluids, and particularly from liquid and
gaseous hydrocarbons and carbon dioxide. The absorbent primarily comprises
ferrous carbonate, desirably obtained from the mineral siderite, and is used for
removing hydrogen sulfide, mercaptans, dimethyl disulfide and other sulfur-
containing compounds from gaseous hydrocarbon streams, light liquid hydrocarbon
streams such as natural gas liquids ("NGL"), crude oil, acid-gas mixtures, carbon
dioxide gas and liquid, anaerobic gas, landfill gas, geothermal gas, and the like.
Methods for making and using the absorbent for sulfur removal are also disclosed.
2. Description of Related Art
[0002] Because of the noxious, toxic and corrosive nature of sulfur-containing
compounds, many different products and methods have previously been disclosed
for use in removing such compounds from liquid and gaseous streams. One such
commercially available product is SULFATREAT® brand particulate reactant that is
said to be useful for removing hydrogen sulfide and other sulfur contaminants from
gases and liquids including, for example, hydrocarbon fuels and geothermal steam
for sale to producers of natural gas and the like. SULFATREAT® is a federally
registered trademark of M-l L.L.C. of Houston, Texas, and, in stylized form, of Gas
1

Sweetener Associates, Inc. of Chesterfield, Missouri. The SULFATREAT® material
has a proprietary formulation but is believed to comprise primarily ferric oxide
particles having a high surface area. Iron sponge is another commercially available
material composed of ferric oxide distributed on wood chips that is being used for
sulfur removal in industrial processes,
[0003] Other iron-containing compositions and methods for removing sulfur
from gas and liquid streams are disclosed, for example, in United States Patent Nos.
4,008,775; 4,344,842; 4,366,131; 4,476,027; 4,705,638; 4,956,160 and 5,948,269.
U.S. 5,948,269, for example, discloses a process for the removal of dissolved
hydrogen sulfide and other malodorous compounds from aqueous liquid or sludge
waste systems such as found in sewage collection and treatment works; industrial
and commercial waste systems, natural and manmade polluted impoundments or
waterways, and septic systems, by use of "alkaline iron." As used in U.S. 5,948,269,
"alkaline iron" refers to an alkali with a variety of iron compounds including ferrous
carbonate.
2

SUMMARY OF THE INVENTION
[0004] The absorbent and method disclosed herein are particularly effective
for absorbing hydrogen sulfide, mercaptans, dimethyldisulfide and other sulfur-
containing compounds from natural gas, light hydrocarbon streams such as natural
gas liquids, crude oil, acid gas mixtures, carbon dioxide gas and liquid, anaerobic
gas, landfill gas, geothermal and other sulfur-containing streams. According to a
preferred embodiment of the invention, the subject absorbent comprises ferrous
carbonate, most preferably siderite granules or powdered siderite that is extruded or
otherwise aggregated, compacted or formed into pellets, prills or spheroids using a
minor effective amount of moisture and, optionally, a binder such as calcium
aluminate cement or another similarly effective material.
[0005] According to another embodiment of the invention, an absorbent bed
is disclosed for use in removing sulfur from gas, liquid or mixed gas and liquid
streams. Examples of sulfur-containing compounds removed by the absorbent
include hydrogen sulfide, mercaptan-containing compounds, organic disulfides and
carbonyl sulfide. The absorbent bed desirably comprises a three-dimensional array
of closely spaced pellets, prills, or otherwise-manufactured aggregates comprising
from about 50 to about 100 weight percent ferrous carbonate, most preferably in the
form of particulate siderite (90% through 100 mesh) aggregated using a binder
comprising from about two to about ten weight percent calcium aluminate cement.
According to a particularly preferred embodiment of the invention, the absorbent
comprises dried extrudates containing about 95 weight percent siderite and about 5
weight percent calcium aluminate cement.
[0006] According to another embodiment of the invention, an absorbent
material is made by mixing about 95 parts by weight particulate siderite (90%
through 100 mesh), about 5 parts calcium aluminate cement, and about 20 parts
water; compacting the mixture by extrusion or otherwise to produce larger particles,
pellets or prills, and thereafter drying the absorbent for a sufficient time to reduce the
moisture content to a moisture level less than about three weight percent. According
to a particularly preferred embodiment of the invention, the absorbent pellets have a
diameter of about 3/16 inch, a length of about 5/16 inch, and are dried at about
120°F for about four hours.
[0007] According to another embodiment of the invention, sulfur is removed
from a liquid, gas, or mixed gas and liquid stream comprising sulfur-containing
3

compounds by causing the stream to pass through an absorbent bed consisting
essentially of particulate material comprising from about 70 to about 100 weight
percent ferrous carbonate, preferably in the form of aggregated particulate siderite.
The absorbent bed most preferably comprises a plurality of pellets comprising from
about 70 to about 100 weight percent ferrous carbonate in combination with an
amount of a binder such as calcium aluminate cement that is sufficient to hold the
absorbent in a desired physical configuration for a desired service life. It will be
appreciated by those of ordinary skill in the art upon reading this disclosure that the
amount of the inventive absorbent that is needed in the absorbent bed will depend
upon factors such as the absorbent particle size, the bed density, the effective
surface area of the absorbent particles, the amount of ferrous carbonate in the
absorbent that is available to absorb the sulfur-containing compounds, and the
temperature, pressure, velocity and residence time of the gas or liquid stream being
treated as it passes through the bed.
[0008] According to another embodiment of the invention, ferrous carbonate
absorbent that has become blackened is periodically regenerated by contacting the
blackened ferrous carbonate with air or another oxygen-containing gas and steam.
Such blackening is believed to be caused by the formation of ferrous sulfide on the
surface of the ferrous carbonate during the removal of sulfur from a liquid, gas, or
mixed gas and liquid stream comprising sulfur-containing compounds.
[0009] According to another embodiment of the invention, sulfur is removed
from a liquid, gas, or mixed gas and liquid stream comprising sulfur-containing
compounds by combining the stream with oxygen and water vapor prior to feeding
the stream to a bed of ferrous carbonate. This method is particularly preferred for
use in removing sulfur from acid gases.
[0010] According to another embodiment of the invention, sulfur is removed
from a liquid, gas or mixed gas and liquid stream comprising sulfur-containing
compounds by passing the stream through a bed of ferrous carbonate in a moist air
environment By subjecting the ferrous carbonate to moist air or another oxygen-
containing gas and water vapor during absorption, the ferrous carbonate is believed
to be continuously regenerated by a catalytic effect, ultimately producing elemental
sulfur that can be easily separated from the process stream.
[0011] According to another embodiment of the invention, a method is
disclosed for removing hydrogen sulfide evolved during natural gas drilling
4

operations, the method comprising adding to a drilling mud used in said drilling
operations from about 40 to about 400 pounds of a finely ground particulate
absorbent (particles passing through a 100 mesh screen), preferably comprising
from about 50 to about 90 weight percent ferrous carbonate, per ton of drilling mud.
No binder is needed or desirable when the finely ground ferrous carbonate is added
to drilling mud according to this embodiment of the invention.
5

DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] Applicant has discovered that ferrous carbonate, preferably in the
form of the mineral siderite, is an excellent absorbent of hydrogen sulfide, carbonyl
sulfide, organic disulfides, mercaptans and other sulfur-containing compounds that
are present in various naturally occurring or synthesized gases and liquids, and
particularly, in gaseous and liquid hydrocarbons and carbon dioxide. Siderite
predominantly comprises ferrous carbonate, and is usually found naturally in
combination with some calcium, magnesium or manganese. For use in the
compositions and various methods of the invention, the siderite can be sourced in
the form of chunks, granules, or finely divided powder. If sourced in chunks, the
chunks are desirably reduced to granules of a suitable size or powdered prior to use.
For use in bed applications, extrudates, as described below, or comparably sized
siderite granules obtained from natural ores are preferred. If siderite is sourced in
the form of a finely ground powder, the powder is desirably agglomerated and
extruded or otherwise shaped prior to use, except when intended for use in
applications such as drilling muds, where the use of siderite powder is recommended
without prior agglomeration to form larger particles.
[0013] In some cases, merely adding up to about 20 weight percent water to
the siderite powder, with mixing, will provided sufficient agglomeration to permit
powdered siderite to be extruded into pellets of suitable size or strands that, when
dried and subsequently handled, will be friable or easily broken into granules that are
satisfactory for use in absorption beds through which sulfur-containing liquids or
gases can be passed or circulated for sulfur removal. In some cases, the use of a
minor effective amount of a binder, most preferably a cementitious material as
further described below may be desirable for use in agglomerating finely divided
ferrous carbonate powders.
[0014] Although it will be appreciated upon reading this disclosure that
ferrous carbonate can be synthesized, the use of ferrous carbonate obtained in
naturally occurring siderite mineral ores is preferred for economic reasons. Hawley's
Condensed Chemical Dictionary (Twelfth Edition) reports that siderite ores naturally
occur in Vermont, Massachusetts, Connecticut, New York, North Carolina,
Pennsylvania, Ohio and Europe.
[0015] Extrudates useful in the absorbent bed of the invention can be
prepared by mixing powdered siderite with a minor effective amount, such as about 5
6

weight percent of the total, of a binder such as calcium alumlnate cement or another
similarly effective material that does not significantly detract from the ability of the
siderite to absorb sulfur or sulfur-containing compounds from a gas or liquid stream.
A preferred calcium aluminate cement for use in the invention is marketed under the
trademark FONDU® by Lafarge Aluminate of Chesapeake, Virginia. According to a
particularly preferred embodiment of the invention, about 5 parts by weight calcium
aiuminate cement is blended into about 95 parts by weight siderite powder (90%
through 100 mesh) to distribute the cement throughout the siderite.
[0016] About 20 parts by weight water per 100 parts by weight of blended
siderite and cement is desirably admixed with the solids to hydrate the binder and
facilitate the formation of larger aggregates, which are then dried to a desired
moisture content. Most preferably, the siderite, cement and water mixture is extruded
and chopped, such as by use of a rotary pelletizer, or otherwise divided or broken,
into extrudates having a diameter of approximately 3/16 inch and a length of
approximately 5/16 inch. The extrudates produced from powder as described above
are desirably dried at a temperature of about 120°F for about four hours. Although
the required drying time can vary according to the size and dimensions of the pellets,
the drying temperature and the humidity of the ambient air, the moisture content of
the aggregated solids is desirably reduced to less than about three weight percent
during the drying stage.
[0017] The absorbent and method disclosed herein are particularly effective
for absorbing hydrogen sulfide, mercaptans, dimethyldisulfide and other sulfur
compounds from natural gas, light hydrocarbon streams such as NGL, crude oil, acid
gas mixtures, carbon dioxide gas and liquid, anaerobic gas, landfill gas, geothermal
and other sulfur-containing streams. For most applications, the sulfur-containing
fluid to be treated is passed through a bed of the subject absorbent pellets or
granules that are disposed inside a vessel such as a cylindrical tower. The amount
of absorbent that is needed in the absorbent bed will depend upon many factors
such as the sulfur content in the feed, the desired sulfur content in the effluent, the
desired lifetime of an absorbent charge, the absorbent particle size, the bed density,
the effective surface area of the absorbent particles, the amount of ferrous carbonate
in the absorbent that is available to absorb the sulfur-containing compounds, and the
temperature, pressure, velocity and residence time of the gas or liquid stream being
treated as it passes through the bed. For some applications, such as the treatment
7

of sour gases encountered during well drilling operations, granulated siderite
absorbent that passes through a 100 mesh sieve can also be beneficially used by
combining it with another material such as drilling mud being pumped into a well.
[0018] Although extrudates having dimensions ranging from about 1/16 inch
to about 1/4 inch are a particularly preferred form for use of the subject absorbent, it
will be appreciated that granules of suitable size can be produced by pulverizing
siderite chunks in a hammer mill or by using other commercially available devices
well known to those of ordinary skill in the art, and thereafter screening to a suitable
particle size range preferably not exceeding about 5/16 inch. Similarly, where
siderite powder or synthetically produced ferrous carbonate powder is the starting
material, means other than extrusion can also be used for agglomerating or
densifying the powder for use in various sulfur removal processes. Such other
means include, for example, hydraulically actuated presses or other compaction
devices. In most cases, minor effective amounts of a binder and water are desirably
added to the powdered siderite or ferrous carbonate to facilitate agglomeration of the
individual mineral particles into larger solid bodies, provided that the binder does not
too greatly reduce the effective surface area of the absorbent.
Representative Siderite Analysis
[0019] A processed siderite composition having a bulk density of 110 pounds
per cubic foot, a specific gravity of 3.63 and a particle size of 90% through 100
mesh, has the following analysis:
8

wt%
Fe (elemental) 43.00 %
FeCO3 86.87
SiO2 5.50
AI2O3 1.30
CaO 0.56
MgO 0.53
S 0.40
Mn 0.35
Cu 0.30
Co 0.02
Cd 0.0041
Pb 0.0001
As 0.00005
Sb 0.00005
Fe2O3
Sample A
[0020] To demonstrate the utility of the invention, a finely divided siderite
powder (90% through 100 mesh) was blended with calcium aluminate cement in a
ratio of 95 parts siderite to 5 parts cement by weight. Approximately 20 parts by
weight water were blended with the siderite and cement mixture, and the mixture
was then extruded to produce a plurality of extrudates having a diameter of about
3/16 inch and a length of about 5/16 inch. These extrudates were dried at 120
degrees F. for four hours to a moisture content less than about 3 wt. %.
Sample B
[0021] Another siderite material was produced by obtaining chunks of siderite
ore approximately 3 to 4 inches in diameter and grinding them to produce granular
particles comprising about 90 wt.% ferrous carbonate and ranging in size from about
1/8 inch to about % inch. Dirt and other contaminants were removed from the
granulated siderite using a sieve.
[0022] The usefulness of the absorbent materials, when prepared as
described above, for removing sulfur from gas and liquid streams containing
sulfurous compounds is further described and explained in relation to the examples
presented below. All stated inlet and outlet compositions are in parts per million
(ppm). Front end sulfurs are stated in ppm of the sulfur-containing compound by
weight of the fluid stream. Thiols are stated in ppm of the respective thiol by weight
9

of the fluid stream. (Some decimal values throughout the Tables below are rounded
due to space considerations.)
Example 1
[G023] A stream of carbon dioxide add gas was charged at a rate of about 60
mis per minute in an upflow direction through a vertical iron pellet treater containing
a bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 68 deg. F
and the treater pressure was 200 psig. The inlet and outlet compositions of the gas
are set forth in Table 1 below:
Table 1

Inlet 1.8 225.9 1.7 6.3 126.6 78.1 2.3
Outlet 0.5 2.7 0.9 13.2 86.0 58.2 1.7
% Reduction 74.0 98.8 50.2 -111.5 32.1 25.5 24.4
Example 9
[0031] A stream of natural gas was charged at a rate of about 60 mis per
minute in an upflow direction through a vertical iron pellet treater containing a bed
approximately 8 inches high and 2 inches in diameter of the Sample A extrudates
prepared as described above. The treater temperature was 130 deg. F and the
treater pressure was 500 psig. The inlet and outlet compositions of the gas are set
forth in Table 9 below:
Table 9

Example 10
[0032] A stream of natural gas was charged at a rate of about 60 mis per
minute in an upflow direction through a vertical H2S absorbent treater containing a
bed approximately 8 inches high and 2 inches in diameter of the Sample B granules
prepared as described above. The treater temperature was 130 deg. F and the
treater pressure was 500 psig. The inlet and outlet compositions of the gas are set
forth in Table 10 below:
Table 10

[0034] A stream of natural gas liquid was charged at a rate of about 40 mis
per minute in an upflow direction through a vertical Iron pellet treater containing a
bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 52 deg. F
and the treater pressure was 500 psig. The inlet and outlet compositions of the gas
are set forth in Table 12 below:
Table 12

bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 60 deg. F
and the treater pressure was 500 psig. The inlet and outlet compositions of the gas
are set forth in Table 14 below:
Table 14

bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 52 deg. F
and the treater pressure was 500 psig. The inlet and outlet compositions of the gas
are set forth in Table 16 below:
Table 16

Example 19
[0041] A stream of carbon dioxide gas was charged at a rate of about 40 mis
per minute in an upflow direction through a vertical iron pellet treater containing a
bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 52 deg. F
and the treater pressure was 500 psig. The inlet and outlet compositions of the gas
are set forth in Table 19 below:
Table 19

Example 21
[0043] A stream of carbon dioxide gas was charged at a rate of about 40 mis
per minute in an upflow direction through a vertical iron pellet treater containing a
bed approximately 8 inches high and 2 inches in diameter of the Sample A
extrudates prepared as described above. The treater temperature was 60 deg. F
and the treater pressure was 500 psig. The inlet and outlet compositions of the gas
are set forth in Table 21 below:
Table 21

Table 22
Treater Sample
Points COS Front
H2S End Sulfurs
CS2 DMDS Methyl Thiols
Ethyl 1-Propyl
Inlet 6.5 23.9 25.7 19.3 44.2 70.2 12.5
Outlet 6.1 0.01 1.3 0.7 0.01 0.6 0.4
% Reduction 5.4 100 95.0 96.1 100 99.1 96.7
[0045] The foregoing examples demonstrate the removal of hydrogen sulfide,
thiols (mercaptans), disulfides and carbonyl sulfide from NGL liquid and from the
gaseous hydrocarbons and carbon dioxide. Dimethyidisulfide (DMDS) can also be
removed by absorption using the compositions and method of the invention. The
increase in DMDS observed in some of the examples is believed to be the result of
oxidative sweetening reactions in which a small amount of oxygen dissolved in the
treated fluid was catalyzed by the iron in the absorbent to promote the oxidation of a
small amount of methyl mercaptan to form DMDS plus water.
[0046] Increases in the level of carbon disulfide were also noticed in some of
the examples. The sulfur analyses were done by sulfur chemiluminescence.
Carbon disulfide analysis is very sensitive to the analytical technique used. Since
the level of carbon disulfide is very low in the feed, small changes in composition can
cause large errors. Errors can also occur because carbon disulfide often
contaminates the feed lines, which can thereafter release small amounts of carbon
disulfide without notice. When the feed lines were freshly replaced, no reduction in
the carbon disulfide content of the fluid stream was measured, and it is believed that
little or no carbon disulfide was removed by the absorbent.
[0047] The data from Tables 1 and 2 demonstrate that both forms of the
absorbent, extrudates (Sample A material) and granules (Sample B material),
remove essentially all of the hydrogen sulfide from a CO2 acid gas stream at ambient
temperatures. About half the carbonyl sulfide was removed over both physical forms
of the absorbents. The thiols (mercaptans) were also removed at high levels over
the granules (99-100%) and over the extrudates (78-96%).
[0048] The data from Tables 3-6 demonstrate that 99 to 100% of the
hydrogen sulfide can be removed from natural gas at ambient temperatures using
the absorbent and method of the invention. The data further demonstrate the
22

removal of 78-100% or the teros, along with some removal of both carbonyl sulfide
and DMDS from the treated fluids.
[0049] Comparison of Tables 3-6 (70°F data) with Tables 7-8 (100°F data)
and Tables 9-10 (130°F data) shows the effect of temperature. The data
demonstrate that 99 to 100% of the hydrogen sulfide is removed at all temperatures
using the subject absorbent and method. The thiol removal decreased with
increasing temperatures, suggesting that the thiols are desorbing at the higher
temperatures. Conversely, the removal of carbonyl sulfide and DMDS increased
with increasing temperatures within the ranges tested.
[0050] The tests done using a gaseous carbon dioxide feed demonstrate that
increasing the pressure from 200 psig (see Tables 1 and 2) to 500 psig (see Tables
15 through 22) appears to aid in the absorption of the thiols. DMDS was 95 to 96%
removed at the higher pressure, in comparison to 20 to 72% removal at 200 psig.
[0051] NGL liquids tend to be low in hydrogen sulfide concentration. Without
competition from hydrogen sulfide, the thiols are removed at levels ranging from 86
to 96% (see Tables 11, 12, 13 and 14). Since oxygen is soluble in this kind of
hydrocarbon, the production of DMDS in some the runs may be attributable to the
oxidative conversion of small amounts of methyl thiol to DMDS as noted above.
[0052] Following use in the iron pellet treater, the Sample A material was
removed and examined. The extrudates were uniformly dark from the edge to center
after having absorbed 1.2 weight percent sulfur, by weight of the extrudate, from the
treated fluid. This observation suggests the occurrence of an exchange reaction
during use that causes the sulfur to migrate toward the center of the absorbent.
Based upon the composition of the absorbent, the dark (black) color is believed to be
ferrous sulfide. The removed extrudates became hot (>135 °F) while sitting out at
room temperature, suggesting that the used material is pyrophoric. After sitting out
overnight, the used material returned to a lighter brown color more similar to that of
the original, pre-use extrudates.
[0053] The general conclusion to be drawn from the data presented above is
that siderite, whether in the form of granules or in the form of extrudates made from
siderite powder, is an excellent absorbent for hydrogen sulfide, thiols (mercaptans),
DMDS and carbonyl sulfide in a variety of feed streams. When the reaction
conditions favor hydrogen sulfide removal, i.e., higher temperatures and pressures,
23

the thiol removal decreases. the thiols are removed more favorably when the
hydrogen sulfide level is low in the feed, at low temperatures, and at high pressures.
[0054] Ferrous carbonate absorbent that has become blackened can be
regenerated periodically by contacting the blackened ferrous carbonate with air and
steam. Such blackening is beiieved to be caused by the formation of ferrous sulfide
on the surface of the ferrous carbonate during the removal of sulfur from a liquid,
gas, or mixed gas and liquid stream comprising sulfur-containing compounds.
[0055] According to another method of the invention, sulfur is removed from
a liquid, gas, or mixed gas and liquid stream comprising sulfur-containing
compounds by combining the stream with oxygen and water vapor prior to feeding
the stream to a bed of ferrous carbonate. This method is particularly preferred for
use in removing sulfur from acid gases but is not preferred for use in natural gas
streams because of the economic disadvantages in subsequently separating the air
and hydrocarbons.
[0056] Alternatively, sulfur can be removed from a liquid, gas or mixed gas
and liquid stream comprising sulfur-containing compounds by passing the stream
through a bed of ferrous carbonate in a moist air environment. By subjecting the
ferrous carbonate to moist air or to oxygen and water vapor during absorption, the
ferrous carbonate is believed to be continuously regenerated by a catalytic effect
ultimately producing elemental sulfur that can be easily separated from the process
stream. Siderite is also a particularly preferred ferrous carbonate material for use as
the absorbent in practicing these methods of the invention.
[0057] The following additional Examples demonstrate the efficacy of
removing sulfur from an acid gas stream combined with air by passing the stream
through a bed of ferrous carbonate in the form of siderite pellets. In each example,
the treater was 24 inches high and 2 inches diameter, and had a treater bed L/D
ratio of 4:1 with catalyst/absorbent bed dimensions of 8 inches high by 2 inches
diameter.
Example 23
[0058] A stream of acid gas mixture containing 93.596% air, 6.328% carbon
dioxide and 0.076% hydrogen sulfide with an inlet gas moisture content of 120.4
Ibs/MM SCF was charged at a rate of about 30 mis per minute in an upflow direction
24

through a vertical iron pellet ireater containing a bed of SULFURTRAP 3/16 inch
siderite pellets. The treater temperature was 100 deg. F and the treater pressure
was 100 psig. The inlet and outlet compositions of the gas are set forth in Table 23
below:
Table 23

WO 2007/035435 r PCT/US2006/035911
through a vertical iron pellet treater containing a bed of SULFURTRAP 3/16 inch
siderite pellets. The treater temperature was 100 deg. F and the treater pressure
was 100 psig. The inlet and outlet compositions of the gas are set forth in Table 25
below:
Table 25

pressure was 100 psig. The inlet and outlet compositions of the gas are set forth in
Table 38 below:

Table 38
Treater Sample
Points COS Front End Sulfurs
H2S CS2 DMDS Methyl Thiols
Ethyl 1-Propyl
Inlet 1.14 4378.5 3.71 0.01 1.39 0.31 0.01
Outlet 1.84 0.03 3.26 0.01 0.01 0.01 0.01
% Reduction -61.5 100.0 12.0 0.0 99.3 96.8 0.0
[0074] Other alterations and modifications of the invention will likewise
become apparent to those of ordinary skill in the art upon reading this specification in
view of the accompanying drawings, and it is intended that the scope of the invention
disclosed herein be limited only by the broadest interpretation of the appended
claims to which the inventor is legally entitled.
33

[0075] We claim:
1. An absorbent for sulfur-containing compounds disposed in streams of
gas, liquid, or mixed gas and liquid, the absorbent comprising ferrous carbonate as
its principal absorptive component.
2. The absorbent of claim 1, comprising from about 50 to about 100
weight percent ferrous carbonate.
3. The absorbent of claim 2, comprising about 95 weight percent ferrous
carbonate.
4. The absorbent of claim 2, further comprising from about 2 to about 10
weight percent of a binder.
5. The absorbent of claim 4, comprising about 5 weight percent of a
binder.
6. The absorbent of claim 1 wherein the ferrous carbonate is in the form
of the mineral siderite.
7. The absorbent of claim 6 wherein the siderite is in the form of granules.
8. The absorbent of claim 6 wherein the siderite is in the form of
agglomerates.
9. The absorbent of claim 6 wherein the siderite is in the form of
extrudates.
10. The absorbent of claim 4 wherein the binder is calcium aluminate
cement.
11. The absorbent of claim 7 where the granules have particle sizes
ranging between about 1/16 inch and about 5/16 inch.
34

12. The absorbent or ciaim 9 wherein the extrudates have a length not
exceeding about 5/16 inch.
35

13. An absoroent for me removal of sulfur-containing compounds from
streams of gas, liquid, or mixed gas and liquid, the absorbent comprising from about
50 to about 100 weight percent ferrous carbonate.
14. The absorbent of claim 13 having the form of agglomerated and
densified powder.
15. The absorbent of claim 13 wherein the ferrous carbonate is siderite.
16. The absorbent of claim 15 wherein the siderite is in the form of
granules.
17. The absorbent of claim 15 wherein the siderite is naturally occurring.
18. The absorbent of claim 14 having the form of particles selected from
the group consisting of pellets, prills, spheroids and granules.
19. The absorbent of claim 15 comprising powdered siderite in combination
with a binder.
20. The absorbent of daim 19 wherein the binder is caldum aluminate
cement.
21. The absorbent of daim 19 comprising from about 50 to about 100
weight percent siderite, from about 2 to about 10 weight percent binder, and a
moisture content less than 3 weight percent.
22. The absorbent of daim 19 wherein the powdered siderite has a partide
size of about 100 mesh.
23. The absorbent of claim 14, made by blending powdered siderite and
calcium aluminate cement in the presence of water, and thereafter extruding, sizing
and drying the resultant product.
36

24. A method for making an absorbent for removing sulfur-containing
organic compounds from gaseous or liquid fluids by providing from about 50 to about
100 parts by weight of ferrous carbonate having a particle size of about 100 mesh,
by bfending with the ferrous carbonate from about 2 parts by weight to about 10
parts by weight cementitious binder and from about 15 to about 25 parts by weight
water, by extruding the blended ferrous carbonate, cementitious binder and water to
produce an extrudate of desired length, and by thereafter drying the extrudate to a
moisture content less than 3 weight percent of the dried extrudate.
25. The method of claim 24 wherein the ferrous carbonate is siderite.
26. The method of claim 24 wherein the cementitious binder is calcium
aluminate cement.
27. The method of claim 25, wherein about 5 parts by weight cementitious
binder and about 20 parts by weight water are blended with about 95 parts by weight
siderite powder.
28. The method of claim 27 wherein the siderite powder is about 100
mesh.
37

29. A method for removing sulfur-containing compounds from a gaseous or
liquid fluid by providing an absorbent principally comprising ferrous carbonate and by
contacting the ferrous carbonate with the fluid.
30. The method of claim 29 wherein the ferrous carbonate is siderite.
31. The method of claim 30 wherein the absorbent is in the form of pellets
made from a blend of powdered siderite and a cementitious binder, together with
sufficient water to hydrate the cement.
32. The method of claim 30 wherein the pellets comprise from about 70 to
about 100 weight percent siderite and from about 2 to about 10 weight percent
cementitious binder.
33. The method of claim 31 wherein the cementitious binder is calcium
aluminate cement.
34. The method of claim 31 wherein the pellets are extruded.
35. The method of claim 31 wherein the pellets are dried to a moisture
content less than 3 weight percent.
36. The method of claim 29 wherein the sulfur-containing compounds are
selected from the group consisting of hydrogen sulfide, carbonyl sulfide, organic
disulfides and mercaptans.
37. The method of claim 31 wherein the pellets are arranged in a bed.
38. The method of claim 37 wherein the fluid is selected from natural gas,
light hydrocarbon streams, crude oil, acid gas mixtures, gaseous carbon dioxide,
anaerobic gas, landfill gas, and geothermal fluids.
38

39. The method or claim 29 wherein the fluid is sour gas inside a well bore
and wherein the ferrous carbonate is finely divided and is distributed in a drilling mud
that is circulated through the well bore.
39

40. A method for regenerating ferrous carbonate absorbent used to
remove sulfur-containing compounds from a liquid, gas, or mixed gas and liquid
stream by periodically contacting the absorbent with air and steam.
41. A method for removing sulfur from a liquid, gas, or mixed gas and liquid
stream comprising sulfur-containing compounds by combining the stream with an
oxygen containing gas and water vapor prior to feeding the stream to a bed of
ferrous carbonate absorbent.
42. The method of claim 41 wherein the stream comprises add gases.
43. A method for removing sulfur from a liquid, gas or mixed gas and liquid
stream comprising sulfur-containing compounds by passing the stream through a
bed of ferrous carbonate in a moist air environment.
44. A method for continuously regenerating a ferrous carbonate absorbent
used to remove sulfur from a liquid, gas or mixed gas and liquid stream comprising
sulfur-containing compounds by subjecting the ferrous carbonate to moist air or to
oxygen and water vapor during absorption.
45. The method of claim 44 wherein the sulfur is removed as elemental
sulfur.
40